In a forum with ten reasonable conversation threads and one highly controversial one, attention is likely to move towards the controversial topic.
The phrase "don't feed the trolls" is well-intentioned but it's difficult to scale the message when so many people are online and can witness and partake in minor and major conversations alike.
It also doesn't help that engagement (regardless of reason for engagement and any human stress created as a result; they're harder for software and metrics to capture) tends to be seen as something to optimize for, both within companies themselves and also by their investors.
Controversial conversations are sometimes necessary. People who repeatedly raise controversial topics to gain notoriety or attention are generally not - although their behaviour may be a sign that they need help in other ways.
